Suction actuated fuel pump



Allg' 25 1954 H. svENDsEN 3,145,659

SUCTION ACTUATED FUEL PUMP Aug. 25, 1964 l l. H. svENDsEN 3,145,559

SUCTION ACTUATED FUEL PUMP Filed Aug. 3l, 1962 4 Sheets-Sheet 2 l/a A SMM ./'b E. iwniim ug- 25, 1964 x. H. svi-:NDSEN 3,145,659

sUCTIoN ACTUATED FUEL PUMP Aug 25, '1964 H. svENDsEN sUcTIoN ACTUATED FUEL PUMP 4 Sheets-Sheet 4 Filed Aug. 5l, 1962 United States Patent O ce 3,145,659 SUCTIGN ACTUATED FUEL PUMP lb H. Svendsen, Milwaukee, Wis., assigner to Briggs & Stratton Corporation, Milwaukee, Wis., a corporation of Delaware Filed Aug. 31, 1962, Ser. No. 220,844 14 Claims. (Cl. 10S-37) This invention relates to pumps and has as its purpose to provide an improved fuel pump especially adapted for use on small portable single-cylinder engines.

More specifically, the purpose of this invention is to provide an improved suction actuated diaphragm type pump wherein rapidly recurring flexure or vibration of a diaphragm produced bythe pressure pulsations in the venturi or fuel supply passage of the engine carburetor effects the pumping action.

Suction actuated diaphragm pumps have been and now are being used on small single cylinder engines-both two and four cyclebut heretofore the height to which fuel could be lifted with such pumps without seriously reducing the power delivered by the engine, was rather limited. This was because the suction that can be developed in the venturi of a carburetor depends upon the extent to which its throat constricts the passage, and constriction reduces the power of the engine. lf the engine were operated at only one speed, or through only a small range of speeds, and at a relatively uniform load, existing diaphragm-type pumps could no doubt be designed to lift fuel higher than they now do, but because of the wide range of speeds and loads under which these engines are expected to operate, it has been impossible with the suction actuated diaphragm-type fuel pumps heretofore available, to reliably lift fuel more than a few inches.

By contrast, this invention provides a suction actuated diaphragm-type pump which lifts fuel several times as high as previously possible, and without detracting from the power delivered by the engine, or in anywise altering the design or proportions of the carburetor.

The fuel requirements of an engine vary with the speed at which it is running, and since the differential between the reduced pressure in the ventri of the carburetor and atmospheric pressure, which obtains during the intake stroke of the engine and which provides the force that operates a diaphragm-type pump, also varies with changes in engine speeds and load conditions and often is least when maximum fuel delivery is needed as when the engine is operating at a slow speed with a Wide open throttle due to a heavy load, it is obviously difficult to design a suction operated pump that reliably meets all requirements. In fact, pumps in which the same diaphragm serves both as actuator and displacement member of the pump, at times will not deliver sufficient fuel, and if the fuel must be lifted any appreciable height, will deliver no fuel at all.

With a View towards overcoming these deficiencies of prior suction actuated diaphragm pumps, this invention has as its specific purpose and object to provide a fuel pump of this general type wherein the available forcepressure differential due to engine suction-is multiplied in its effect upon the pumping diaphragm.

Also, with a view to keeping the quantity of fuel delivered by the pump more uniform during running conditions, and making it possible to quickly prime the carburetor after a dry fuel tank has been refilled, this invention has as another of its objects to provide a pump in which the maximum volume of the pumping chamber is automatically increased whenever the available force exceeds a predtermined value, as when the choke valve is closed as it might be during cranking.

With the above and other objects in view which will 3,145,659 Patented Aug. 25, 1964 appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiments of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of the physical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a longitudinal sectional view through a fuel pump embodying this invention, and illustrating the same at the instant it has completed its delivery stroke or impulse;

FIGURE 2 is a View similar to FIGURE 1, but illustrating the elements of the pump at completion of an intake stroke or impulse in response to suction of a magnitude less than a predetermined value;

FIGURE 3 is a view similar to FIGURES 1 and 2, but showing the elements of the pump at the completion of an intake stroke or impulse produced by suction of a magnitude greater than that which produced the intake stroke or impulse in FIGURE 2;

FIGURE 4 is an exploded or separated perspective view of the main elements of the pump shown in FIGURES 1-3, inclusive;

FIGURES 5, 6 and 7 are longitudinal sectional Views, like FIGURE 1, but illustrating three different modifications of the invention; and

FIGURE 8 is a cross sectional view through the venturi tube of a carburetor and a fuel tank directly therebeneath, as in the Brown et al., Patent No. 2,529,242, illustrating the pump of this invention mounted thereon; and

FIGURE 9 is an exploded or separated perspective View of the main parts of the pump shown in FIGURE 8.

Referring now particularly to the accompanying drawings, and considering first the structure shown in FIG- URES 1-4, inclusive, the pump-as distinguished from its suction-responsive actuating means-comprises a body 5 having a wall surface 6 which is preferably fiat, and a cavity 7 which opens to the surface 6 so that the edge or rim 8 of the cavity is at the surface 6.

Overlying the surface 6 is a pumping diaphragm 9 of flexible fabric-like material, capable of withstanding rapidly recurring flexure and not affected by gasoline and the additives it might contain. The medial portion of the diaphragm 9 extends across the mouth of the cavity 7 and coacts therewith to form a pumping chamber 10. Inlet and outlet passages 11 and 12, respectively, formed partially in the body 5, lead to and from this pumping chamber.

The peripheral portion of the pumping diaphragm 9 is held in sealing engagement with the contiguous portion of the body 5 by being clamped between it and an annular spacer 13 which also holds the peripheral portion of an actuating diaphragm 14 in sealing engagement with the rim of a cup-shaped body 15, for which purpose the rim of the cup-shaped body 15 is flat. This assembly is held together by screws 16.

Preferably, the inside 17 of the cup-shaped body is round and the hole 18 through the spacer 13 is also round and of the same diameter as the mouth of the cupshaped body.

It is significant that the inside diameter of the cupshaped member and hence the diameter of the diaphragm 14 which extends across its mouth, is considerably greater than the diameter of the mouth of the cavity 7. This makes the area of the actuating diaphragm 14 much greater than the area of the medial portion of the pumping diaphragm which extends across the mouth of the cavity 7.

The inlet and outlet passages 11 and 12 extend or pass through the spacer 13, as at 11a and 12a, and are completed by outer end portions 11b and 12b in the cupshaped body 15, these outer end portions being connectible respectively with a fuel tank and the fuel inlet of a carburetor, both not shown.

The chamber 19 which is formed jointly by the cupshaped member 15 and the actuating diaphragm 14 is connectible with a source of suction as for instance the venturi tube of a carburetor, through a port 20 in the bottom of the member 15. Hence the underside of the actuating diaphragm 14 is subjected to whatever negative pressure obtains in the chamber 19, while the top side thereof is at all times subjected to atmospheric pressure since the space between the two diaphragms is open to atmosphere through a hole 21 drilled through the spacer 13.

The medial portions of the two diaphragms are connected so that they flex in unison. Whatever means is employed to effect this connection, obviously must do so without making the diaphragms susceptible to leakage of either liquid or air. This may be done by clamping the medial portion of both diaphragms against the top of an inverted cup-shaped collar 22, as by the head of a clamping screw 23 passed through aligned holes in the center of the diaphragms and threaded into the collar 22, with a washer 24 interposed between the head of the screw and the adjacent surface of the pumping diaphragm 9.

A compression spring 25, which preferably is of the conical helical type, is interposed between the collar 22 and the bottom of the cup-shaped member 15. Since the collar 22 is smaller in diameter than the mouth of the cavity 7, the spring 25 yieldingly projects the medial portion of both diaphragms into the cavity 7, as shown in FIGURE 1; and in moving the same to this position expels any liquid in the cavity through the outlet passage 12.

Flexure of both diaphragms in the opposite direction against the force of the spring 25, and in response to a pressure differential at opposite sides f the actuating diaphragm due to the existence of negative pressure inside the chamber 19 expands the volume of the pumping chamber 7 and draws liquid into it from a supply thereof connected to the inlet passage 11; and upon cessation of negative pressure in chamber 19, the spring 25 again projects the medial portion of the diaphragms into the cavity 7 to expel the liquid therefrom.

Since this pumping action is produced by the spring 25 which is inside the cup-shaped member and negative pressure manifested therein, the chamber 19 may be regarded as a working chamber.

It is, of course, understood that the inlet and outlet passages 11 and 12 are provided with check valves, and preferably these check valves are provided by flaps 26 and 27, which are integral parts of the diaphragms 9 and 14, respectively. When the check valve 26 opens, it enters a pocket 28 in the body 5, and when the valve 27 opens it enters a pocket 29 in the cup-shaped body 15; when closed the valves 26 and 27 lie flat against the adjacent surfaces of the spacer 13.

The fact that the space between the two diaphragms is at all times communicated with atmosphere (through the hole 21) makes two important results possible. First, it makes it possible to have the very necessary pressure differential at opposite sides of the actuating diaphragm 14 every time the working chamber 19 is communicated with a source of suction; and second, it holds the pumping diaphragm 9 tightly against the surface 6 of the body 5 when negative pressure obtains within the pumping chamber 7. In so doing, the atmospheric pressure between the two diaphragms coacts with the spring 25 to hold the pumping diaphragm 9 in sealing engagement not only with the edge 8 of the cavity 7, but also with the entire area of the surface 6 lying between the edge of the cavity and the edge of the hole 18 in the spacer 13.

This area of the surface 6 surrounding the mouth of the cavity 7, thus may be considered a seat for the pumping diaphragm, and as long as the pumping diaphragm is engaged with this seat, flexure of the pumping diaphragm is confined to its medial portion which closes the mouth of the cavity 7, so that the maximum volume of the pumping chamber is definitely less than it can be if the pumping diaphragm is partially or completely off that seat.

In operation, when the underside of the actuating diaphragm 14 is subjected to a suction impulse derived from the intake stroke of an engine and manifested in the venturi tube of the engine carburetor with which the port 20 is connected, the resulting pressure differential at opposite sides of the actuating diaphragm 14 forces the diaphragm 14 down into the working chamber 19, as shown in FIGURE 2, and in so doing flexes the medial portion of the pumping diaphragm downwardly or outwardly to expand the volume of the pumping chamber and draw fuel into it.

As long as the magnitude of the pressure differential acting upon the diaphragm 14 is below a predetermined value, the pumping diaphragm is not drawn away from the edge of the cavity 7 and the pump operates with the maximum volume of the pumping chamber being defined by the size of the cavity and the extent that the medial portion of the pumping diaphragm flexes outwardly without leaving the edge of the cavity. However, when the pressure differential acting upon diaphragm 14 exceeds that predetermined value and, as a result, the diaphragm 14 is pulled farther down into the working chamber-as shown in FIGURE 3-the pumping diaphragm is drawn away from the edge of the cavity 7 and progressively away from its engagement with its seat formed by the Wall surface 6. The volume of the pumping chamber is thus correspondingly increased so that a greater quantity of fuel will be pumped with each cycle of operation of the pump, it being understood that, in every instance, upon cessation of suction in the working chamber, the spring 25 pushes the connected diaphragms back and expels the liquid in the pumping chamber.

Although the diaphragms 9 and 14 have peripheral portions which, as stated, are clamped against the opposite faces of the spacer 13, only those portions of the diaphragms which are circumscribed by the edge of the hole 18 in the spacer should be considered diaphragms in the sense that the term is used herein from the standpoint of effecting the pumping action. These portions of the two diaphragms are, of course, of the same diameter and substantially the same area. However, despite the fact that their areas are substantially the same, the effective area of the pumping diaphragm is much smaller than that of the actuating diaphragm 14, as long as the pumping diaphragm is in sealing engagement with the edge of the cavity 7. This is a very important feature of the invention. Because of it, the available force, i.e., the magnitude of the pressure differential which obtains when the working chamber is connected to a source of suction, is multiplied in its effect upon the pumping diaphragm.

To illustrate, assume that it requires vacuum on the order of ve inches of mercury to lift fuel from the level of the fuel tank into the pumping chamber 7, and that the available suction produces a vacuum equal to only three inches of mercury. Under these conditions, the pressure differential resulting from the available suction applied to a diaphragm having only the area of the medial portion of the pumping diaphragm which covers the mouth of the cavity 7 would be incapable of lifting the fuel this high, since the ratio between the actuating force and the lifting force would be one-to-one (1:1).

However, because the actuating diaphragm 14 has a much larger area than the area of the medial portion of the pumping diaphragm closing the mouth of the cavity 7, the pressure differential acting thereon and produced by the available force would be ample to effect fiexure of the pumping diaphragm needed to lift the fuel this height for, in this case, the ratio of the actuating force to the required lifting force would be considerably greater than one-toone.

From this it follows that the pump of this invention can be readily designed to deliver an adequate supply of fuel to the engine, without detracting from the power produced by the engine, even when the fuel must be lifted a substantial height, and even when the available suction is minimum, as when the engine is pulling a heavy load and running at slow speed with the throttle valve of its carburetor wide open.

The extent to which the response of the actuating diaphragm to pressure differential acting thereon produces motion of the medial portion of the pumping diaphragm, of course depends upon the magnitude of the pressure differential; and when that differential exceeds a predetermined value-as would be the case during cranking of the engine with the choke valve of the carburetor closed-the actuating diaphragm will be pulled far enough into the working chamber to withdraw the pumping diaphragm from its sealing engagement with the edge of the cavity 7 and away from its seat provided by the wall surface 6 encircling the cavity, as shown in FIGURE 3. This increases the maximum volume of the pumping chamber, and increases the quantity of fuel delivered by each pump cycle. Such increased delivery per cycle of pump operation enables the pump to quickly prime the carburetor in the event the fuel tank has run dry and has been refilled.

The modified embodiments of the invention illustrated in FIGURES 5, 6 and 7 are functionally the same as that shown in FIGURES l-4, inclusive, for in each case the effective area of the pumping diaphragm is considerably smaller than the effective area of the actuating diaphragm as long as the available force (pressure differential) acting on the actuating diaphragm is less than a predetermined value, but when that predetermined value of force is exceeded the effective diameter and, consequently, the volume of the pumping chamber, is increased.

Essentially, the difference between the structures shown in FIGURES 5, 6 and 7 and that of FIGURES l-4, inclusive, is in the omission of the spacer 13 between the peripheral portions of the two diaphragms. Thus, in each of the modified embodiments of the invention shown in FIGURES 5, 6 and 7, the actuating diaphragm 30 is entirely inside the cup-shaped member 15' and has its peripheral portion in sealing engagement with the bottom thereof, while the peripheral portion of the pumping diaphragm 31 is clamped directly between the body 15 and the cover or body member The check valves 32 and 33 controlling the inlet and outlet passages in these structures are both formed by flaps integral with the pumping diaphragm 31.

In the structure illustrated in FIGURE 5, the connection between the medial portions of the two diaphragms comprises a hat-shaped stamping 34, the crown of which protrudes through a hole in the center of the actuating diaphragm 30. Atmospheric pressure in the working chamber 19 which is vented to atmosphere through a hole 21', holds the actuating diaphragm down on the brim 35 of the hat-shaped stamping; and the central portion of the pumping diaphragm 31 is clamped to the top of the crown of this hat-shaped stamping by the head of a screw 36 threaded into the crown. A conical pancaketype compression spring 37 confined between the bottom of the cup-shaped member and the underside of the brim 35 yieldingly urges both diaphragms upwardly and projects the medial portion of the pumping diaphragm into the cavity 7.

That part of the pumping diaphragm 31 which surrounds its medial portion is held against its seat provided by the surface 6 by a light compression spring 38 reacting between the bottom of the cup-shaped member 15 and the underside of a metal washer 39, which substantially covers the area of this portion of the pumping diasor phragm. Thus, in the operation of this embodiment of the invention, before the pumping diaphragm will be drawn out of sealing engagement with the edge 0f the cavity 7', the differential pressure acting upon the diaphragm 31 must be sufficient to overcome the force of the spring 33 as well as atmospheric pressure.

Another way of connecting the two diaphragms is illustrated in FIGURE 6. In this case, a relatively light compression spring 4f) reacts between the bottom of the cupshaped member 15 and the underside of an annular fiange 41 projecting from and forming the brim of an inverted hat-shaped stamping 41. The flange 41 is the functional counterpart of the washer 39 of FIGURE 5. Also, as in the FIGURE 5 structure, the medial portions of the two diaphragms are connected by a hat-shaped stamping 34', the crown 42 of which passes through a hole in the crown portion of the inverted hat-shaped stamping 41; but in this case the medial portion of the pumping diaphragm is yieldingly urged into the cavity 7 by a spring 43 confined between the pumping diaphragm and the crown of the inverted hat-shaped stamping 41 which is supported against the thrust of the spring 43 by the larger spring 4t). Hence, these two springs act in series to effect the discharging fiexure of the pumping diaphragm.

It should be observed that although the connection between the medial portion of the two diaphragms in the structures of FIGURES 5 and 6 is not positive, as it is in the embodiment of the invention shown in FIGURES l-4, inclusive, the forces acting upon the actuating diaphragm will hold its medial portion in sealing engagement with the flange upon which it seats.

The modification shown in FIGURE 7 is more like that of FIGURES 1-4, inclusive, in that the two diaphragms are positively connected to one another to move in unison at all times, but in this case the connection is effected by clamping the medial portions of the two diaphragms to the opposite ends of a collar 45 which spaces the diaphragms from one another, even at their connected medial portions. Also, as in FIGURES l-4, inclusive, the pumping diaphragm in FIGURE 7 is held in sealing engagement with the edge of the cavity 7 by atmospheric pressure, a spring 46 confined between the two diaphragms and the spring 47 which acts upon the actuating diaphragm in opposition to suction applied thereto to produce the discharge stroke of the pump. The spring 46 also serves to hold the edge of the actuating diaphragm in sealing engagement with the side wall of the working chamber 19'.

In FIGURES S and 9, the pump of this invention (and, more specifically, that form thereof shown in FIGURES l-4, inclusive) is mounted directly on a carburetor of the type illustrated in the Brown et al. Patent No. 2,529,- 242. In fact, in this embodiment of the invention, the counterpart of the cup-shaped body is provided by a boss Sti on the side of the venturi tube 51 of the carburetor, the boss having a flat outer surface 52 and a cylindrical cavity 53, the mouth of which opens to the surface 52 and the bottom of which is communicated through a port 54 with the bore 55 of the venturi tube.

The actuating diaphragm 56 overlies the fiat surface 52 and has its medial portion extending across the mouth of the cylindrical cavity 53 to coact therewith in forming the working chamber 57. A spacer 5S having an external configuration corresponding to that of the boss 50, and a hole 59 at least as large in diameter as the cylindrical cavity 53, is interposed between the actuating diaphragm and the pumping diaphragm 60, the space between the two diaphragms being vented to atmosphere by a hole 61 drilled through the spacer.

Overlying the outer face of the pumping diaphragm is a cover 62 which is the counterpart of the body 5 in the structure shown inFIGURES 1 4, inclusive, and the entire assembly is held together by screws passed through aligned holes in the cover, the spacer and the diaphragms, and threaded into the boss 50.

The pumping chamber 63 is formed by a cylindrical cavity 64 in the cover 62 and the overlying portion of the pumping diaphragm 60, and as in the structure of FIGURES 1 4, inclusive, the two diaphragms have their medial portions connected by being clamped between the head of a screw 65 threaded into a cup-shaped collar 66. The collar 66 receives the small end of a conical compression spring 67, the other end of which bears against the bottom of the cavity 53. Accordingly, in the operation of the pump, the spring pushes the connected medial portions of the two diaphragms into the pumping chamber to expel liquid therein, and the differential in pressure at opposite sides of the actuating diaphragm resulting from suction impulses in the venturi tube of the carburetor iiexes the pumping diaphragm in the direction to draw liquid into the pumping chamber.

Since the pump in this case is built into the carburetor, and since the carburetor, as in the aforesaid Brown et al. patent, is directly above the fuel tank 68, the inlet passage 69 which opens to the pumping chamber is provided by cored passages in the cover 62, the spacer 58 and the boss 50, where it connects with a suction pipe 70 which depends from the bottom of the carburetor and extends into the fuel tank with its inlet end near the bottom of the tank.

Also for the same purpose, the outlet passage 71 which leads from the pumping chamber is formed by cored passages in the cover 62, the spacer 5S and the boss 50, to debouche into a reservoir 72 mounted in the upper portion of the fuel tank. From the reservoir 72, the fuel is drawn directly into the venturi tube by suction therein through an inlet passage 73 which leads to the needle valve of the carburetor and with which a short suction tube 74 connects, the mouth of said tube being in the lower portion of the reservoir.

The inlet and outlet passages are, of course, provided with check valves, preferably in the form of flaps 75 and 76 integral with the pumping and actuating diaphragms, respectively.

By mounting the pump on the carburetor as described, the height the fuel is directly lifted by suction in the venturi tube is very short and always the same, since the pump keeps the reservoir full, any overflow simply spilling over the edge of the reservoir and into the tank.

As in the embodiments of the invention before described, the pumping diaphragm remains in sealing engagement with the edge of the cavity 64 and the seat formed by the surrounding ilat surface 64 of the cover, as long as the pressure differential driving the actuating diaphragm is less than a predetermined value, but leaves the same to increase the volume of the pumping chamber when the magnitude of the pressure differential exceeds that predetermined value.

From the foregoing description, taken in connection with the accompanying drawings, it should be apparent to those skilled in this art that this invention provides a fuel pump especially well adapted for use on small portable, single cylinder internal combustion engines, and that the pump of this invention possesses many advantages and improvements over similar pumps heretofore available.

It will also be evident that because of its ability to lift fuel an appreciable height, the pump of this invention lends itself for use on outboard motors where the portable fuel tank or can usually is at a much lower level than the carburetor.

What I claim as my invention is:

l. A fuel pump comprising:

(A) a body having a wall surface and a cavity opening to said surface;

(B) a flexible pumping diaphragm larger than the mouth of the cavity overlying said wall surface and having its medial portion extending across the mouth of the cavity to close the same when the diaphragm is in sealing engagement with the edge of the cavity;

(C) means sealing the peripheral portion of the pumping diaphragm to said body so that the pumping diaphragm and the body together form a pumping chamber of either small or large maximum volume depending upon whether said diaphragm is in sealing engagement with the edge of the cavity or spaced therefrom;

(D) means forming valved inlet and outlet passages leading into and from said cavity;

(E) means yieldingly biasing the pumping diaphragm toward said body and holding the same in sealing engagement with the edge of the cavity so that the maximum volume of the pumping chamber is normally small, and only said medial portion of the pumping diaphragm is operative to effect pumping;

(F) a pulsation motor operable upon being energized by fluid pressure pulsations to effect reciprocating motion of a magnitude proportional to the magnitude of the energizing pressure pulsations; and

(G) means drivingly connecting said motor with the medial portion of the pumping diaphragm to flex it back and forth without disturbing the sealing engagement between said diaphragm and the edge of the cavity as long as the magnitude of the fluid pressure pulsations by which the motor is energized is less than a predetermined value, but to withdraw said pumping diaphragm from its sealing engagement with the edge of the cavity and thus increase the maximum volume of the pumping chamber and the displacement of the pump when the magnitude of the uid pressure pulsations energizing the motor is in excess of said predetermined value.

2. The fuel pump of claim l, wherein element F comprises:

(A) an actuating diaphragm larger in area than the mouth of said cavity; and

(B) means to subject one side of said actuating diaphragm to atmospheric pressure and the other side thereof to intermittent suction impulses.

3. The fuel pump of claim l, wherein element E comprises:

(A) an annular member covering the portion of the pumping diaphragm which overlies the wall surface surrounding the mouth of the cavity; and

(B) a compression having one end thereof anchored and its other end bearing against said annular member to urge the same towards said wall surface.

4. The fuel pump of claim l, wherein the side of the pumping diaphragm opposite that which faces the wall surface of the body is at all times subjected to atmospheric pressure, so that dur-ing periods of negative pressure in the cavity, atmospheric pressure assists the yielding biasing means (element E) in maintaining the diaphragm in sealing engagement with the edge of the cavity.

5. A fuel pump comprising:

(A) a body having a wall surface and a cavity opening to said surface;

(B) a pumping diaphragm larger than the mouth of the cavity overlying said wall surface with its medial portion extending across the mouth of the cavity;

(C) means sealing the peripheral portion of the pumping diaphragm to the body so that (l) the pumping diaphragm and said body coact to form a pumping chamber of either small or large maximum volume depending upon whether the diaphragm is in sealing engagement with the edge of the cavity or spaced therefrom;

(D) means forming valved inlet and outlet passages leading to and from the cavity so that llexure of the pumping diaphragm alternately draws liquid into and expels it from the pumping chamber in an amount depending upon the extent and frequency of such flexure;

(E) an actuating diaphragm larger than the mouth of the cavity;

9, (F) means connecting the medial portions of said two diaphragms for movement in unison so that said diaphragms are disposed in tandem relation, and flexure of the actuating diaphragm imparts flexure to the pumping diaphragm;

(G) biasing means acting upon the medial portion of the diaphragms to yieldingly Hex both of them toward said body and thereby cause the pumping diaphragm to expel any liquid in the pumping chamber;

(H) means for subjecting the entire area of the side of the actuating diaphragm which is remote from the pumping diaphragm to intermittent suction impulses; and

(I) means whereby the facing sides of the two diaphragms are at all times exposed to atmospheric pressure so that the pumping diaphragm (1) is held against said wall surface and in sealing engagement with the edge of the cavity as long as the pressure differential at opposite sides of the actuating diaphragm during the intermittent suction impulses is less than a predetermined value, but

(2) is drawn away from the edge of the cavity and the surrounding wall surface when said pressure differential exceeds said predetermined value,

(3) whereby the volume of the pumping chamber varies with the magnitude of said pressure differential.

6. The fuel pump of claim 5, wherein element H comprises:

(A) a cup-shaped body, the rim of which has the peripheral portion of the actuating diaphragm sealed thereto; and

(B) means providing a port leading to the interior of said cup-shaped body and through which the same may be connected with a source of suction impulses.

7. The fuel pump of claim 5, wherein element I comprises:

(A) an annular spacer interposed between the peripheral portions of the two diaphragm, the spacer having (l) an air passage therethrough connecting the space between the diaphragms with the atmosphere.

8. The fuel pump of claim6, wherein the biasing means (element G of claim 5) comprises:

(A) a compression spring confined between the means connecting the two diaphragms and the bottom of the cup-shaped body.

9. The fuel pump of claim 7, wherein (A) the inlet and outlet passages pass through the spacer and the peripheral portions of the diaphragm, and wherein (B) the valve of the inlet passage is a flap integral with one of said diaphragms and the valve of the outlet passage is a ap integral with the other diaphragm.

10. In a suction-actuated fuel pump:

(A) structure defining a pumping chamber having valved inlet and outlet ports;

(B) a flexible pumping diaphragm forming one wall of the pumping chamber;

(C) means fixed with respect to said structure forming an annular seat for the pumping diaphragm encompassing a medial area thereof;

(D) yieldable means to normally hold the pumping diaphragm on said annular seat and thus (1) define the normal maximum volume of the pumping chamber and (2) confine flexure of the pumping diaphragm to said medial area thereof;

(E) an actuating diaphragm larger in area than said medial area of the pumping diaphragm and at the side of the pumping diaphragm remote from said seat thereof;

(F) means connecting the medial portions of said diaphragms for ilexure in unison so that ilexure of the actuating diaphragm in one direction imparts iiexure to the pumping diaphragm tending to carry it off of its seat,

(G) the larger area of the actuating diaphragm as compared to said medial area of the pumping diaphragm enabling a pressure differential insufficient to eect pumping flexure of said pumping diaphragm if applied to said medial area thereof, to produce such pumping flexure when applied to the actuating diaphragm; and

(H) means to subject the side of the actuating diaphragm which is remote from the pumping diaphragm to intermittent suction impulses while the opposite side thereof is subjected to atmosphere, so as to (l) produce intermittent flexure of the actuating diaphragm and pumping ilexure of only said medial area of the pumping diaphragm as long as the magnitude of the suction impulses is less than a predetermined value and to (2) produce greater exure of the actuating diaphragm and in turn withdrawal of the pumping diaphragm partly off of its seat to thus correspondingly enlarge the maximum volume of the pumping chamber when the magnitude of the suction impulses exceeds said predetermined value,

(3) whereby the maximum volume of the pumping chamber is governed by the magnitude of the suction impulses acting upon the actuating diaphragm.

11. In a suction actuated fuel pump:

(A) a pumping diaphragm operable upon back and forth exure thereof to lift and deliver fuel with each ilexure cycle, in an amount dependent upon the area of said diaphragm that is so flexed;

(B) an actuating diaphragm responsive to intermittent pressure differential at opposite sides thereof to produce reciprocating motion of a magnitude depending upon the magnitude of said pressure differential;

(C) means drivingly connecting the actuating diaphragm with the medial portion of the pumping diaphragm so that the reciprocating motion produced by the former imparts iiexure to the latter; and

(D) means to confine the flexure of the pumping diaphragm to a medial area thereof which is smaller than the area of the actuating diaphragm, as long as said pressure differential is less than a predetermined value While allowing a greater area of the pumping diaphragm to be flexed when said pressure differential exceeds said predetermined value, said last named means comprising (1) means forming an annular seat encompassing only said medial area of the pumping diaphragm and adapted to have one side of said diaphragm engaged therewith;

(2) means to subject the opposite side of the pumping diaphragm to atmospheric pressure; and

(3) biasing means pressing against said opposite side of the pumping diaphragm at the center of its medial area.

12. The structure of claim 11, wherein element C thereof secures the medial portions of the two diaphragms together for movement in unison.

13. The structure of claim 11, wherein said annular seat has a surface of substantial area encircling the opening it denes; and further characterized by (A) an annular plate engaging the opposite side of that portion of the pumping diaphragm which is substantially coextensive in area with said surface of the seat; and

(B) biasing means acting on the annular plate to press the same towards said surface of the seat and thus yieldingly hold the contiguous portion of the pumping diaphragm thereon.

14. The structure of claim 13 further characterized by:

(A) means on said annular plate forming a spring seat facing the central portion of the pumping diaphragm and spaced axially therefrom; and wherein (B) said biasing means which presses against the pumping diaphragm at the center of its medial area is con- 10 fined between said spring seat and the pumping diaphragm.

References Cited in the ile of this patent UNITED STATES PATENTS 2,133,207 Mennesson Oct. 11, 1938 2,621,595 Burks Dec. 16, 1952 FOREIGN PATENTS 632,401 France Jan. 9, 1928 

1. A FUEL PUMP COMPRISING: (A) A BODY HAVING A WALL SURFACE AND A CAVITY OPENING TO SAID SURFACE; (B) A FLEXIBLE PUMPING DIAPHRAGM LARGER THAN THE MOUTH OF THE CAVITY OVERLYING SAID WALL SURFACE AND HAVING ITS MEDIAL PORTION EXTENDING ACROSS THE MOUTH OF THE CAVITY TO CLOSE THE SAME WHEN THE DIAPHRAGM IS IN SEALING ENGAGEMENT WITH THE EDGE OF THE CAVITY; (C) MEANS SEALING THE PERIPHERAL PORTION OF THE PUMPING DIAPHRAGM TO SAID BODY SO THAT THE PUMPING DIAPHRAGM AND THE BODY TOGETHER FORM A PUMPING CHAMBER OF EITHER SMALL OR LARGE MAXIMUM VOLUME DEPENDING UPON WHETHER SAID DIAPHRAGM IS IN SEALING ENGAGEMENT WITH THE EDGE OF THE CAVITY OR SPACED THEREFROM; (D) MEANS FORMING VALVED INLET AND OUTLET PASSAGES LEADING INTO AND FROM SAID CAVITY; (E) MEANS YIELDINGLY BIASING THE PUMPING DIAPHRAGM TOWARD SAID BODY AND HOLDING THE SAME IN SEALING ENGAGEMENT WITH THE EDGE OF THE CAVITY SO THAT THE MAXIMUM VOLUME OF THE PUMPING CHAMBER IS NORMALLY SMALL, AND ONLY SAID MEDIAL PORTION OF THE PUMPING DIAPHRAGM IS OPERATIVE TO EFFECT PUMPING; (F) A PULSATION MOTOR OPERABLE UPON BEING ENERGIZED BY FLUID PRESSURE PULSATIONS TO EFFECT RECIPROCATING MOTION OF A MAGNITUDE PROPORTIONAL TO THE MAGNITUDE OF THE ENERGIZING PRESSURE PULSATIONS; AND (G) MEANS DRIVINGLY CONNECTING SAID MOTOR WITH THE MEDIAL PORTION OF THE PUMPING DIAPHRAGM TO FLEX IT BACK AND FORTH WITHOUT DISTURBING THE SEALING ENGAGEMENT BETWEEN SAID DIAPHRAGM AND THE EDGE OF THE CAVITY AS LONG AS THE MAGNITUDE OF THE FLUID PRESSURE PULSATIONS BY WHICH THE MOTOR IS ENERGIZED IS LESS THAN A PREDETERMINED VALUE, BUT TO WITHDRAW SAID PUMPING DIAPHRAGM FROM ITS SEALING ENGAGEMENT WITH THE EDGE OF THE CAVITY AND THUS INCREASE THE MAXIMUM VOLUME OF THE PUMPING CHAMBER AND THE DISPLACEMENT OF THE PUMP WHEN THE MAGNITUDE OF THE FLUID PRESSURE PULSATIONS ENERGIZING THE MOTOR IS IN EXCESS OF SAID PREDETERMINED VALUE. 